Method and means for controlling compasses



April 6, F A WADE El AL METHOD AND MEANS FOR CONTROLLING COMPASSES lFiled June 6, 1932 5 Sheets-Sheet 1 April 6,4 1937. -F. A. WADE ET AL2,076,328

METHOD AND MEANS FOR CONTROLLING COMPASSES Filed June s, 1952 .5sheets-sheet 2 v IN VEN TOR. FRANC/5 A. WADE ADOLF URFER.

J7 l ATTORNEY April s, 1937.

F. A. WADE El' AL METHOD AND MEANS FOR CONTROLLING COMPASSES Filed Junee, 1952 5 sheetssheet 3 Tf1-q E F/PANC/S ,4. WADE ATTORNEY 5 Shees-Sheel4 Aprll, 1937. F. A. WADE ET Al.

METHOD AND MEANS FOR CONTROLLING COMPASSES Filed June 6; 1932 nbu..

April 6, 1937. F.r A. WADE Er AL METHOD AND MEANS FOR CONTROLLINGCOMPASSES 5 sheets-sheet 5 Filed June 6, 1932 Tlf R.E. ma n NAR N EWF. RWA. m CF NL Mw FA Patented Apr.- 6, 19377 UNITED sTATEs `PA'rENr OFFICE.

'METHOD AND MEANS Fon` coNTnoLLmG coMrAssEs Francis A. Wade, Brooklyn,and Adolf Urfer, Richmond Hill, N. Y., assignors to Bendix AviationCorporation, South Bend, Ind., a corporation of Delaware ApplicationJune s, 1932, serial 10.615320 36 Claims. (Cl. 33-222) 10 andcombinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements,combinations and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting'a parthereof, illustrate one embodiment of the invention, and together withthe description, serve to explain the principles of the invention.

Fig. 1 is a longitudinal vertical section of a mechanism embodying apreferred form af our invention;

Fig. 2 is a transverse vertical section taken on line 2 2 of Fig. 1;

Fig. 3 is an enlarged fragmentary horizontal section on line '3 3 ofFig. l;

Fig. 4 is a transverse vertical section on line i 4 4 of Fig. 1, lookingtoward the left;

Fig. 5 is a transversevertical section of a modiiled embodiment of theinventionshowing the magnetic compass controlled by an azimuthgyroscope;

Fig. 6 is a fragmentary enlarged vertical sec-- tion taken on line 6-6of Fig."5; l

Fig; '7 is a fragmentary view similar ,to Fig. 5,

showing another 'modification wherein gyroscopic control is periodicallyapplied to the compass;

Fig. 8 is a modified form of the mechanism of lo Fig. 5, showingthecompass-controlling clutch actuated by electrical means which arecontrolled independently of the azimuth gyro; and

Fig. 9 is a view similar to Fig. 8, but showing `an electrical timingcontrol for the compass L5 clutch.

; deviations to which a magnetic compass is subject when mounted in aconveyance or vehicle.

The invention is especially directed to providing f methods and meansfor controlling a magnetic compass during periods when the vehicle isturning or is deviatingfrom a set condition or course,

The invention also includes they novel combina' I tion of a freedirectional gyroscope, a compass card rotatably mounted adjacent saidgyro's'cope,

a driving element on the gyroscope to turn in azimuth therewith andhaving a mechanical driving connection with said card to turn the latteras the gyroscope turns relative to its mounting,

and means whereby said driving connection may be interrupted withoutdisturbing the gyroscope.-

More specifically, the invention seeks to control magnetic compasses invehicles so that the errors generated by turning movements of thevehicle are automatically prevented from registering on .the compassindicating means, sothat the compass will always be orientedsubstantially cor-v rectly, regardless of the attitude or motion of thevehicle. For this purpose, our inventionprovides a magnetic compasswhich normally is permitted to respond freely to the magnetic inearthmagnetic field, while during turns the com- 2 pass is maintained incorrectly oriented relation by interposing an external or non-magneticcontrol factor which prevents or compensates for the deviations inducedby the turning movements.

One object of our invention is to eliminate the 30 well-knownnortherlyturning error to'whlch all magnetic compasses are subject. 'I'heinvention further provides` a compass which is always orientedsubstantially correctly and so can be used 'for steering the vehicleregardless of the course or the movements of the vehicle, and whereinthe correct reading always appears on the same single indicating member.

In its present preferred embodiments, the external or` non-magneticcompass control is de- '40 rived from gyroscopic means which aresensitive to turning -movements of the 'v vehicle. The variouswell-known and peculiar characteristics of the gyroscope are employedfor creating the desired compensating control factors. Broadly, the

invention comprises the gyroscopic control of magnetic -compasses forlimited periods while leaving the compass free for response Itoearthmagnetic iniluences outside said periods- O rdinarily andpreferably, the gyroscopic effect is 5 v'utilized solely during turningmovements of the compass-containing vehicle, and directly corrects orcompensates for the errors and deviations which the turning movementscreate. However,

the gyroscopic control may also be applied under other circumstances andrelations, as, for example, by periodic timed applications of thecontrolling element so as to check and damp out compass deviations andthus maintain a substantially correct orientation thereof.

The invention is adapted for magnetic compasses generally, especiallywhen used in vehicles or` moving conveyances such as ships, land veyhicles'and air craft. Probably the greatest eld for the invention is inits application to aerial navigation. The great speed andmaneuverability of airplanes subject their magnetic compasses to seriouserrors during the rapid changes of course of the plane, frequentlygiving a compass reading which is temporarily far from the true magneticcourse of the plane. By virtue of our invention, the compass indicatesthe true course of the plane at all times, substantially regardless ofthe deviation effects introduced by centrifugal forces, angularvelocities, acceleration forces and the like.

Theforegoing general description and the following detailed descriptionas well, are exemplary and explanatory of the invention but notrestrictive thereof.

Referring now in detail to the present preferred embodiments of theinvention, shown by wayof illustration in the accompanying drawings, ashereinbefore stated, dierent characteristics or effects of the gyroscopeare preferably utilized for controlling the magnetic compass. In Figs.1, 2, 3 and 4, a preferred embodiment of the invention is shownillustrating the employment of the precession effect of the gyroscope toprevent or compensate for errors induced in the magnetic compassreadings. y

The invention provides a magnetic compass of the conventional liquidtype (Fig. 1) comprising the graduated compass card I suitably mounted Yin the body of damping liquid 2 and provided with the usual magnetic orsensitized bars 3 and 4 suitably suspended on either side of the cardcenter.- The compass card is provided with a suitable pivotbearing III,preferably of the conventional Jeweled type, formed on the top of thevertically disposed' stud II. lA pivot pin I2 is centrally mounted inthe compass card by means of pin housing I3, the pointed lower end ofsaid pin fitting in andsupporting the compass card upon the bearing I0.

It will be understood that the novel features of our invention areparticularly adapted for magnetic cbmpasses employed in steeringvehicles, especiallyin aerial navigation. Accordingly, the magneticcompass is indicated as mounted in a suitable housing or frame I5 andforming part ofl the instrument assembly of the vehicle. In an airplane,for example, the longitudinal axis of the mechanism shown in Fig. l (l.e., the axis lying in the plane of the paper) will preferably becoincident with the fore-and-aft airis of the plane, while thereading-lens, I@ of the liquid compass willy be in the instrument panelof the plane.

` Thus the magnetic compass will be oriented with respect to thefore-and-aft axis of the plane and will thereby be effective for directcourse laying and steering. The compass will be provided with a suitablelubber line Il interposed between the reading glass and the compass cardand seated in the base of the housing I5.

As indicated, the magnetic compass will be provided with the usualnecessary structure for its support and maintenance in the` vehicle. Asembodied, the housing I5 comprises a substantially complete reservoirfor the dmping liquid around the compass card while the reading lens I6is suitably securedto the outer face of the reservoir as by peripheralplate I8 and screws I9. The liquid reservoir may also be provided withthe usual baiile plate mounted above the compass card near the surfaceof the liquid, and having a central opening 2I. X preventing the cardfrom leaving its pivot bearing may be suspended over the top of the pinbushing I3 by hangers 23 attached to the baille plate 20.

Referring now to the means for`non-magnetically controlling themovements and indications of the compass card during selected intervals,especially for the correction and prevention of errors due to movementsof the vehicle, in the embodiment shown in Fig. 1, means are illustratedfor employing the precession action of a gyroscope for the purposesstated. Briefly, in the present embodiment we utilize substantially theconstruction and operating principles of the well-known gyroscopicturn-indicator employed in modern aircraft. The precession movements ofthe gyroscope which take place during turning movements of the vehicleare proportional to and constitute a measure of the angular movement ofA canopy 22 for the vehicle. By our invention we provide means duringturns and meansfor utilizing the precessive movement thereof tocompensate for the deviations induced in the compass. reading by saidturning movementsf Referring nowin detail to the gyroscope constructionand the linkage thereof to the compass, a gyroscope (Figs. 1 and 2) isprovided having a rotor 25 with a normally horizontal axis 2B, said axisbein'g'parallel to the lateral or transverse axis of the vehicle. In thepresent embodiment, the gyroscope is mountedfor two degrees of freedom,the rotor axis 26 being rotatably mounted in the horizontal gimbal ring21, while said gimbal ring is rotatable aboutl a fixed horizontalfore-and-aft axis, being suit ably suspended on the fixed pivot members28 and 29. Said pivot members comprise pointed, threaded pins suitablyjournaled in the frame extension 30 of the instrument housing I5,4 andin the vertical interior bracket 3|, respectively. It wi1l,be clear thatthe gyroscope is thus rotatable about the fore-and-aft axis of thevehicle, while the rotorv is also rotatable about its horizontaltransverse axis 26.

The rotor of the gyroscope may be driven by any suitable or conventionalmeans such as an electro-magnetic drive. In the present preferredembodiment, however, the rotor is shown driven by an air blast throughnozzle 3l which is seated in the bottom of the instrument casing anddirects its blast substantially tangentially against the varies 32 onthe periphery of rotor 25. The nozzle is variably positionablevertically with respect to the rotor, having an exterior threadedsurface which engages a cooperatingly threaded socket in the casing 30.Air under pressure may be supplied to nozzle 3| exteriorly of the casingfrom any suitable source (not shown) such as an air pump, or a Venturitube. Suitable openings 33 are provided in the casing 30 for permittingescape of` air from the casing. l

Means are provided for centralizing the gyroscope and maintaining therotor axis normally horizontal. As embodied, a segmental plate '35 isfixed to the gimbal ring 21 at the pivot point 29, so as to turn withthe gimbal ring as the .latter rotates about its ifore-and-aft axis. A

aovaazs centralizing spring 'device comprising spring nnger 36 is fastat one end`to the :door of housing 30, while the-freeen'd thereof isconnected radially to the bottom of plate 35 by a verticallydisposedcoil spring 31 fast to a pin 38 near the periphery of the plate. Whilewe have shown spring means for centralizing the gyrosco'e, it will beunderstood that a pendulum kor other suitable centralizingmeans may beemployed. In the gyroscope construction shown in Figs. 1 and 2, it willbe clear that a turning movement of the vehicle will induce a precessionof the gyroscope about the fore-and-aft axis of the gimbal ring 21. vForexample, with the direction of rotation of the rotor shown in Fig. l, aclockwise turn of the-airplane about its rudder axis will induce aprecession of the gyroscope rotor in counter-clockwise sense viewed inthe direction in which the ship is flying or in the direction of 0 Fig.2. That is, if the airplane makes a righthand turn, the gyro rotor willtilt, the upper edge of the rotor moving downwardly to the left in Fig.2, while the lower edge of the rotor moves upwardly and to the right.'On the other hand, 5 if the ship describes a left-hand turn, the gyrowill precess in the opposite sense.

It will further be understood that the amount of force of the precessionwill be directly proportional to the angular velocity or rate of'turn of0 the ship, and that the duration of the precession will be coincidentwith the ships turning.' The centralizing spring will operate to opposethe precession movements and will instantaneously return the rotor axis26 to horizontal when turning ceases. Y y

'I'he invention comprises means for linking the precession movements ofthe gyroscope tothe compass so that during turning movements of the shipthe compass will be subjected to gyro- 5 scopic control. As embodied,clutch means are provided for gripping the compass card at the instantthe ship commences to turn, the clutch electrical means, but it will beunderstood that the clutch actuation and control from the gyroscope maybe effected by straight mechanical linkage; by hydraulic; pneumatic orother suitable transmission means.

As shown, the lower portion 40 of the pin bushing or housing I3 on thecompass card is globu-I lar and the outer surface thereof constitutesthe driven member of the clutch mechanism hereinafter described. A pairof cooperating clutch-r ing-jaws or g'rippers 4I are mounted on theupwardly and outwardly inclined arms 42A of apair of bell cranks whichare pivotally supported on'the upper surface of a pinion 43 whichsurrounds and is loosely revolvable about the compass-supporting studII. to the base of the casing I5, the lower end -44 of the stud beingscrew-threadedinto a suitable socket insaid base. A shoulder-45 on thestud bears against the upper surface of said base and forms a supportingseat for the pinion 43. The upper surface of the pinion is cut away nearthe periphery to provide an inner raised platforml 46 (Fig. 3) forsupporting the bell crank pivots 41, whereby the horizontal lever arms48 of the bell cranks project radially outwardly beyond The stud Il isfixed l the raised platform and overlie the indented peripheral surfaceof the pinion. Coil springs 48 are attached to the underside of eitherarm comprises an annular coil or solenoid which l0 is mounted in a ring56 and held above the arms 48 of the bell cranks by suitable brackets51. The solenoid is of such diameter that it loosely surrounds the studII and the outwardly and upwardly inclined lever arms 42, while theouter 15 ends of lever arms 48 underlie the solenoid and are providedwith magnetizable armature members 58. It will be clear thatenergization of the solenoid will draw the members 58 upwardly therebythrowing the gripping member 4I into 20 contact with driven member 40.

Means are provided for energizing thevsolenoid, and in accordance withthe invention, said energization is controlled by the precession of theS'yroscope. As embodied, circuit wires 60 and 6I 25 lead from thesolenoid, through suitably insulated supports to a battery 64, or othersuitable source of electrical energy. Wire 60 is grounded to the metalcasing at 65, while wire 6I leads to contact f post 66 in rear of theplate 35 and just above leaf 30 spring 36, the fixed end of which islikewise grounded to the frame at 61. \It will be clear that spring 36and post 66 or a normally open switch in the solenoid circuit and thatthe switch will be closed and thecircuit energized whenever 35 spring 36is raised -to contact with the post through precession movement of thegyro. Accordingly, the compass card is seized and held by the clutchmembers 4I as soon as the gyroscope precesses in either direction andthe clutch is in, 40

stantly released as soon as precession ceases an the gyro returns tohorizontal.

T'he embodied means for transmitting a corrective or compensating motionfrom the gyro to the compass card during precession of the former .45 c

comprises, broadly, a mechanically actated gearing train adapted todrive or rotate the compass card through means of the. clutch alreadydescribed. The gearing train receives its power from a prime mover ofsuitable construction 50 which is linked to the gearing train to drivethe same through means. controlled by precession of the gyroscope.

In detail, a driven shaft 10 (Figs. 1- and 4)' is A rotatably suspendedfrom the top of the instru- 55 ment housing by suitable brackets 1I andis provided with a keyed bevel pinion 12 at its rear end. Said pinionengages pinion 13 to drive shaft 14, which transmits its motion toshaft. 15

through gears 16 and 11 at the top of the housing. 60

Shaft 14 may be provided with suitable sleeving 18. Shaft 15 extendsvertically through the housing and is `suitably journaled at 19 in thebottom I5 thereof. Pinion 80 is fixed to the lower end ofA shaft 15 andtransmits the rotary move- 65 ment thereof to pinion 43 'throughintermeshing idler LSI. Thus it will be clear that rotaticn of shaft 10is transmitted to pinion 43 through suitable gearing to pinion 43 and,when the solenoid is energized, the clutch will transmit 70 this turningmovement to the compasscard.

Means are provided fo`r rotating shaft 10 ineither direction an amountproportional to theprecessive force of the gyro and coincident with theduration of such precession. As embodied,

two side-by-side ratchet wheels l5 and 88 are mounted on shaft 10 andkeyed to .rotate therewith. These ratchets are formed with their teetharranged in opposite senses, whereby rotary 5 `movement in eitherdirection may be imparted to shaft 10. Diametrically opposed arms 81 and88 are independently mounted on shaft 10 adjacent the ratchet wheels andare loosely rotatable with respect to the shaft. These arms carry lpawls 89 and 90, respectively, at their outer ends and bothpawls arenormally restrained from engagement with their cooperating ratchetwheels 85 and 86. For this purpose, the inner faces of the pawls areformed with suitableindentations l 9|, while the pawls normally overlieand rest upon cooperating pins 92 projecting from the supportingbrackets 11. Furthermore, the arms` 81 and 88 and their pawls arenormally urged away from the ratchet wheels by springs 93 and 94,

` 20 respectively, so that both pawls are normally free from engagementwith their ratchet wheels. Driving force may be transmitted to eitherpawl arm from a continuously operated prime mover such as electric motor95. The drive from the 25 motor to the pawl is preferably intermittentand of limited stroke, and for this purpose an A- shaped frame 96 iseccentricallyattached to the motor shaft, as by the Scotch yokeconnection 91,

whereby the A-frame will oscillate continuously 30 through a definitepath. The A-frame is provided with two actuating fingers 91 and 98projecting beyond its cross-piece, said fingers being l adapted toengage the pawl arms and intermittently advance one pawl or the otherinto engagement with its ratchet wheel. The A-frame mounting and itsstroke are such that both iingers 91 and 98 are normally maintained outof engagement with either pawl arm. However, if the A-frame be raised orlowered from its normal path of oscillation, one of its driving fingers91 or 98 will engage the adjacent pawl arm and the pawl will be pushedalong the pin 92 and into engagement with the ratchet teeth. Theoscillating movement of the finger (98 for example) will then advancethe pawl 92 Vstep-by-step (thereby rotating the vshaft while contactbetween the :tlnger and pawl arm ls maintained. In the meantime, thediametrically opposite pawl is maintained free from engagement with itsratchet wheel and also with the other driving finger of the A-frame.

Means are provided whereby the precession of the gyroscope will lower orelevate the A-frame, thereby bringing llinger 91 .for y98 into contactwith its respective pawl arm 81 or 88.. As embodied, a verticallydisposed arm |05 is pivotally attached to the lower surface of theA-frame 96 preferably by a universal connection such as ball and socketjoint |06. The lower end of arm |05 is similarly connected to the plate35 at |01, said connection being near the upper edge of the semicircularplate 35 and relatively near the periphery thereof, so that .the arm |05will receive a substantial up and down movement when the plate turns.The arm is preferably variable in length, as by a suitable turn bucklejoint |08, to adjust the stroke of the plate 35 with relation to theA-frame 96.

It will be clear that the stroke of the pawl will be proportional to theprecession oi' the gyroscope. That is, when the arm |05 is raised byplate 35, for example, the distance which pawl- 90 will be advanced byfinger 98 depends upon the height to which said nger is lifted. If the75 precession/of the gyro is relatively slight, finger sa will rise onlya sughi; distance and wm contact with arm 88 during only a short portionof its stroke. However, if the nger rises higher, the contact thereofwith arm 88 lasts longer and the stroke of pawl 90 is correspondinglyincreased. Thus'the amount of the precession is reflected in the strokeofthe pawl and the rotation imparted to shaft 10 will be a function ofthe precession and therefore a function of the rate of turnof thevehicle.

, as follows:

, The compass card is normally mounted for free response to the magneticinfluence totheA earth eld and under normal conditions of flight willcorrectly indicate the magnetic course of the vehicle. However, when thecraft or vehicle commences to turn from its straight course, the

gyro immediately precesses an amount prop or-Y tional to the rate ofturn and continues such precession throughout the turning movement. Assoon as turning movement commences, the compass card is seized by theclutch and restrained w vthe oscillating A-frame and such "Contact ismaintained throughout the .turning movement. The pawl and ratchet meansthus effect a rotation of the compass card, through the gear traindescribed, and saidrotation will be in the sense opposite to the compassdeviation induced-by the turning of the vehicle and in an amount equalto said devlation.- Consequently, duringr the entire turning movement,the magnetic compass will continue to register a true course of thevehicle just as though no turning were taking place; As soon as turningmovement and concomitant precession cease, the pawl will' be disengagedfrom the oscillating finger and the rotation of the compass card willcease.

and the compass surrendered wholly to magnetic control.

By virtue of the construction described, substantially all compassdevlationsxchargeable to movement of the vehicle are prevented orcompensated for. For example, northerly turning errors, undueoscillation of the magnetic element, lag in indication and drag of thedamping liquid in the compass are eliminated. The compass can thus beused for steering, regardless of the course or movements of the vehicleand in consequence the accuracy of navigation and the smoothness oftravel are greatly augmented.

Our invention'comprises another embodiment of the basic method andmeansfor non-magnetically controlling a magnetic compass, wherein thecharacteristic "rigidity-in-space or gyroscoplc inertia of a gyroscopeis utilized. In lthis modification of the invention, the errors anddeviations induced in the readings of the magnetic compass by movementsof the airplane or other vehicle are automatically prevented or At thesame instant, the solenoid circuit will be broken compensated for bylinkage to and control from and azimuth gyro i. e., a gyroscope mountedfor three degrees of freedom and therefore adapted to preserve itspredetermined position in space irrespective of turning movements orirregularities in :flight of the plane.

'Ihe present preferred embodiment employing the rigidity-in-spacecharacteristic of the gyro is illustrated in Fig. 5. As embodied, amagnetic compass of the liquid type hereinbefore described is providedhaving the same general features of conventional construction shown inFig. 1, and like reference numerals are applied to similar parts in Fig.5. A generally cylindrical or semiglobular casing is provided forholding the compass and the damping liquid, supporting stud beingmounted in the base of the casing by socket |2| and set screw |22.

An azimuth gyro is mounted above the com- 20 pass and is contained inand supported by an airtight cylindrical casing which ypreferablyconstitutes an integral extension of the compass casing |20. Thegyroscope comprises a rotor |26 set to rotate in a predeterminedvertical plane, 25 which preferably is the vertical plane through thefore-and-aft axis of the airplane. Accordingly the rotor turns on ahorizontal axle, the ends of whichare rotatably supported by horizontalgimbal ring |21. Ring |21`is in turn rotatable about a 'centralhorizontal axis, being supported by suitable ball bearings on axis pins|28 and |29. The supports |28 and |29 are themselves mounted in an outergimbalring |30 which is rotatable about a horizontal axis at rightangles to the plane of the rotor, said ring |30 being rotatablysupported in the exterior gimbal ring |3| at |32 and the diametricallyopposite bearing (not shown). i

The exterior gimbal ring |3| is mounted for rotation about its verticalaxis, for this purpose being provided with a suitable ball bearing |33at its tangency with the top of the casing |25 and is similarlysupported by ball bearing |34 in bushing |35 which is seated in thebottom |36 of said casing.

The rotor of the gyroscope may be maintained in motion by anyappropriate means. As embodied, a pneumatic drive is provided for therotor |26, the interior of casing |25 being maintained below atmosphericpressure by a suction tube |40 which is suitably supported in the wallof casing |25 by screw-threaded connection |4|,.\ The tube |40 may -beconnected t any suitable exhausting means, (not shown) such as a Venturitube, suction pump, or the intake manifold of the vehicle motor. An airnozzle |42 is positioned to drive rotor |26, the periphery of which maybe provided with suitable vanes, as shown in 60 Fig. 2 for example. Thenozzle |42 communicates with the atmosphere by conduit |43 whichprojects upwardly through a suitable central opening in screw-threadedbushing |44 in the top |45 of casing |25. ASuitable 'means are providedfor straining the air admitted to conduit |43, the upper end thereofhaving a screen |46 attached thereto by collar |41. A perforated dome|48 is attached to the top |45 surrounding and protecting the open endof conduit |43. Itwill' be clear that conduit |43 is rotatable withgimbal ring |3| relatively to casing |25. The nozzle', so positioned,a'ssists in centralizing the rotor.

Means are provided for linking the compass card to the hereinbeforedescribed gyro mechanism when relative movement occurs between theA andout of. contact therewith, whereby the compass Acard is normally freefor simple magnetic operation.

However, means are provided for vertically moving member |50 to contactwith and grip the.

compass card, saidrmeans being controlled by movement of the gyroscope.As embodied, member |50 is suspended from vertical rod 55, said rodbeing axially movable in sleeve |56 which constitutes a downwardprojection integral with rotatable gimbal ring |3|. Means for axiallymoving the rod |55 comprises bell crank |51, which is pivotally attachedto the upper end of the rod at |58. The bell crank is pivotally mountedat |59 upon bracket |60, said bracket being fixed to the horizontallydisposed platform |6|. The vertically disposed arm |62 of the bell crankis pivotally joined to the piston rod |63 to which piston head |64 isattached. The piston head is' slidably mounted in piston cylinder |65,said cylinder also being supported upon platform |6| by `interveningblock |66 which is fixed to said platform.

The platform |6| constitutes an integral horizontal extension of gimbalring |3| and is rotatable with said gimbal ring. It will be clear,therefore, that rotation of the gimbal ring |3| with respect to casing|25 will effect rotation of l the piston assembly and rod |55 therewith,while movement'of the piston in its cylinder will cause axial movementof rod |55 and opera-tion of the clutching mechanism. As stated, theclutch is normally disengaged, and for this purpose a helical spring |10enci-rcles the'upper end of rod |55 and is seated in cylindricaldepression |1| in the gimbal ring. A collar |12 is fixed to rod |55 atject to the low pressure in casing |25, through the passage-116 inhousing |11. A suitable opening |18 is provided in the end of cylinder|65,

said opening being in alignment with the mouth of passage |16, butspaced therefrom, so that-theI air blast from conduit |15 may enter thepiston cylinder and force the piston to the left as viewed in Fig. 5.

'I'he invention provides means for permitting actuation of the clutchpiston only when relative movement occurs between the gimbal ring of thegyroscope and the" relatively fixed casing |25. As embodied, thepassageway between conduit |16 and the piston cylinderis normally closedby a valve or interponent |80, said valve `being movable to clear theopening |18 ,in the end of the cylinder` when the gimbal ring, |3|rotates on its vertical axis.

Means for moving the valve |80 comprise an arm |8| (Fig. 6) pivotallysupported at |82 on casing |11 and provided at its lower end with avertical slot |83. A friction roller |84 rides on the iiatupper surfaceof plate |36 of the casingy and is in rotatable engagement with lever|8| through the' roller axle |85 which slides in the slot |83. Acooperating bracket |81 overlies theAroller and extends downwardlyparallel to the outer face thereof, said bracket being verticallyslotted at |88'to receive the outer end of axle |85. Means for normallyholding the lever |8| in valve closing position comprise centeringsprings |90 and |9| which are fixed to the casing block |11 and 10engage the lever upon either side.

K It will be clear that so long as the gimbal ring maintains its normalposition in the vertical plane transverse to the fore-and-aft axis ofthe vehicle, the lever |8| will remain vertical and valve |80 will beclosed. However, if the gimbal ring turns out of its normal transverseplane, thefrictional drag of roller |84 on surface |36 will rock lever|8| and uncover opening |18, thereby permitting the blast of air toenter the piston cylinder and force the piston to the left.

In the operation of the hereinbefore described mechanism, when .theaircraft or othervehicle in which the compass is mounted is following astraight course, the rotor of the gyroscope will lie in the verticalplane through the fore-and-aft axis of the vehicle and the clutch |50will be disengaged, thereby leaving the compass card free toearth-magnetic iniluences. However, when f the vehicle commences toturn., the rigidity-inspace or gyroscopic inertia of the gyroscope willcause the gy'ro to maintain its original position in space, therebyeiecting relative motion between the casing |25 (which is xed to thevehicle) and the platform |6| which is xed to the gimbal ring |3| of thegyro. The relative rotation of platform |5| will be proportional to andin the sense opposite to the turning of the vehicle. At the instant thatturning movement commences, valve |80 will start to open, and the clutch|50 will seize the compass card, thereby subjecting the card to therotational movementof the gyroscope. As a'result, the compass card isprevented from deviating during turning movement of the vehicle, but isseized and maintained on its true magnetic indication throughout theturning movement. When said turning movement ceases, the valve |80automatically closes and the clutch is released, thereby surrenderingthe compass again to the magnetic influence without loss of properindication or undue oscillation of the card.

In the hereinbefore described mechanism for utilizing therigidity-in-space characteristic of the gyroscope, we have shown anddescribed pneumatic means for actuating the gyro and its clutchconnection to the compass. It will be understood,.

movement of the gyro and vehicle.

Our invention comprises a further modication (Fig. 8) wherein theazimuth gyro mechanism l illustrated in Fig. 5 is selectively connectedto control the magnetic compass by means inde-- pendent of the movementsof the azimuth gyro itself. In the present preferred embodimentof thismodification, the clutch which connects the azimuth gyro to the compasscard is controlled independently of the azimuth gyro by means likewisesensitive to turning movements of the vehicle.

As embodied, the clutch is actuated by a solenoid, said solenoid beingenergized through the precession movements of a second gyroscope, whichmay and preferably will be a turn-indicator gyroscope. In its generalaspects, the clutch control of the compass card will be generallysimilar to that shown in Fig. 1.

In detail, the shaft or rod |55 is connected to the gimbal ring |3| ofthe superimposed azimuth gyro shown in Fig. 5 and said shaft |55 isadapted to turn with gimbal ring |3| as hereinbefore described. Theshaft is mounted for axial movement with respect to the gimbal ring,being provided with the helical spring seating |10 described inconnection with Fig. 5. A cylindrical housing 200 forms an integraldownward extension of gimbal ring |3| thereby forming a guide for theshaft, which is provided with a guiding bushing 20| slidable withinthecylindrical housing. -The gimbal ring and shaft assembly are rotatablysupported upon the seating member 202 by ball bearings 203. f

A solenoid coil 205 surrounds the cylindrical housing 200, the axialshaft |55 itself constituting the armature of the solenoid. Theenergizing circuit of the solenoid comprises wires 206 and 201, thelatter communicating with a source of current 208 and thence leading toswitch arm 209 which comprises a leaf spring fixed at one end 2 I0 tothe casing 2|| of the turn-indicator gyroscope. The other circuit wire206 is connected to contact arm 2|5 of the switch, mounted above andnor- 'The gimbal ring is rotatable about thehorizontal fore-and-aft axisthrough supporting pins 223 and is provided with plate 224v whichtransmits precession movements of the gyro to switch arm 209 throughcentering spring 225.

In the operation of the modification shown in Fig. 8, it will be clearthat the shaft |55 through its connection to gimbal ring i 3|, will beturned relatively to casing |25 during turning movements of the vehicle.These turning movements will simultaneously cause the turn-indicatorgyro to precess, thereby energizing the solenoid and closing the clutch|50. Thus the superimposed azimuth gyro will be used solely for turningthe compass card, while the clutch actuation will be controlled by theprecession movement of the turn-indicator. It will be understood thatthe turn-indicator gyro 220, etc., may be the usual turn-indicator usedin aerial navigation and utilized for the clutch control in addition toits indicating action. or, if desired,

a separate or auxiliary gyroscope 220 may be pro-A vided for controllingthe clutch |50 only.

In the hereinbefore described mechanism, we have disclosed methods andmeans for controlling magnetic compasses in direct relation to themovements'of the vehicle. However, our invention further comprises amethod and mechanism for periodically subjecting amagnetic compass toexternal of gyroscopic control independently of the Vehicle movements orother deviating factors. More specifically, we provide means forperiodically applying gyroscopic control to the magnetic compass so asto damp out or regularly and intermittently prevent or compensate fordeviations and uctuations arising in the magnetic compass indications..v

For example, in addition to the relatively large reviations induced inmagnetic compasses by sudden or protracted turning movements of thevehicle, the magnetic elements of the compass are subjected todisturbances and oscillations whenever the vehicle is accelerated ormakes any change in its speed or direction. The liquid surrounding the'compass oscillates and exerts a deviating drag" on the compass card,while local magnetic iniiuences may also cause temporary aberrations inthe Icompass indication.

By our invention, the gyroscope is intermittently and periodicallylinked to the compass card, thereby exerting a steadying inuence uponthe compass at all times. The gyro itself is designed to maintain afixed position in space and thereby indicate a predetermined directionover several `minutes without substantial error. By locking the compasscard to the gyroscope for a given relatively short time period andperiodically releasing it, the direction indicated by the compass cardwill at all times be, substantially the magnetic lheading of thevehicle. and break ofthe gyro contact will permit the compass to respondto the .inuences of the earthmagnetic ileld while it is periodicallystabilized and damped by the gyroscope. .On the other hand, thegyroscope will never be continuously connectedto the compass for aperiod longer than one during which the gyroscope will give accuratedirectional indication.

In Fig. 7 we illustrate oneembodiment of mechanism for periodicallylinking the compass card to the direction-indicating gyroscope. Asembodied, the gyroscope shown in Fig. 7 is of the azimuth gyro typeillustrated in Fig. 5, having three degrees of freedom and driven by anair blast. The same reference numerals applied to corresponding parts inFigs. and '7 and such `parts need not be redescribed in connection withFig. 7. The means for periodically connecting the clutch |50 to theazimuth gyro comprises devices for actuatingthe piston |64 to close andopen clutch |50 through relatively short time intervals. For thispurpose, the air duct |15 is extended upwardly through the surroundingair duct |43 and projects ,above the top thereof into the air dome 230.The admission of air into duct |15 is controlled by a valve 23| which isoperated by suitable timing mechanism `to periodically open and closethe end of the duct. -As embodied,

valve 23| comprises the end of a bell crank lever pivoted at 232and-having its vertical arm 233 in contact with a timing cam 234 on arotating disc .235. Said disc may be continuously rotated at the properspeed by a suitable prime mover (not shown) such asa motor or clockspring. If deE sirable, means may be provided for selectively varyingthe timing interval. The valve 23| is urged to closed position bycompression spring A modified form of mechanism for actuating clutch |50in timed relation between the gyroscope and the compass card shown inFig. 9, comprises anyelectrically operated assembly. As embodied, theclutch may be provided with solenoid- The make linking the compass ltoactuating means similar to those shown and described in connection withFig. 8. The solenoid circuit may be made and broken by a time controlledinterrupter comprising contact lever 250 which closes the circuitbyengagement with contact 25| and is raised into contact therewith by cam252 on timed rotating disc 253. It will be clear that the operation lofthe mechanism in Fig. 9 is substantiallyI the same in principle as thatof Fig. 7.

The invention in its broader aspects is not lim'- ited to the 'specificmechanisms shown and described but departures may be made therefromwithin the scope of the accompanying claims without departing from theprinciples of the invention and without sacrificing its chief'advantages.

What we claim is:-

1. A mechanism for controlling a compass, in-4 mounted in the vehicleand having two degrees of freedom with respect thereto, and meansrespon- .sive to precession movements oi' the gyroscope for controllingthe compass.

2. A mechanism for controlling a compass, including in combination, amagnetic compass mounted in a vehicle and adapted to normally respondfreely to magnetic influences, a gyroscope mounted in the vehicle, adriving member, and means controlled by precession movements of thegyroscope for connecting the compass to said driving member duringturning movements of theyehicle. l l

3. Aomechanism for controlling a compass, including -in combination, amagnetic Vcompass mounted in a vehicle and adapted to normally respondfreely to magnetic inuences, a gyroscope mounted in the vehicle, drivingmeans for rotating the compass in azimuth, and means actuated byprecession of the trolling said driving means.' 4. A mechanism forcontrolling a compass, including in combination, a magnetic compassmounted in a vehicle and adapted to normally respond freely to magneticinfluences, a gyroscope mounted in the vehicle, and means controlled bythe gyroscope for turning the compass in azimuth proportionately toprecession movements of the gyroscope.

5. In an airship, in combination, a magnetic compass vhaving a card, agyroscope having its axis of spin normally horizontal and at rightanglesto the longitudinal axis of the ship, means for rotating the compasscard, and a clutch controlled by means responsive to precessionmovements of the gyroscope for connecting the compass card to therotating means during turning movements of thelship.

6. A mechanism for controlling a compass, including in combinationjamagnetic compass, an

gyroscope for conazimuth gyroscope, and means for selectively thegyroscope.

7. A mechanism for controlling a compass including in combination amagnetic compass mounted in a Vehicle, an azimuth gyroscope andpneumatic means for selectively linking the compass to the gyroscope. I

8. A mechanism .for controlling a compass, in-'I cluding in combinationa magnetic compass, an azimuth gyroscope, and electrical means forselectively linking the compass to the gyroscope.

9. A mechanism for controlling a compass,` in'- cluding in combination,a magnetic compass, an,

v465 by the latter during said movement.

' trolled means for intermittently linking the compass to the gyroscope.

11. In combination, a magnetic compass adapted to be mounted on a craftfor normally free response to influences of the earths magnetic field,directional control means disassociated from the compass, and meanseective upon angular movement of the craft in azimuth for connecting thecompass to said directional means to control the compass during suchmovement to obviate deviations of said compass produced by said angularmovement of the craft which might otherwise occur. l,

12. In combination, a magnetic compass adaptedto be mounted on a craftfor normally free response to influences of the earths magnetic field,gyroscopic directional control means disassociated from the compass, andmeans effective upon angular movement of the craft in azimuth forconnecting the compass to said directional means to control the compassduring such angular movement to obviate deviations of the compassproduced by said angular deviation of the craft which otherwise mightoccur.

-13. A mechanism for controllinga compass, including a magnetic compassmounted in a vehicle and adapted to normally respond to magneticinfluences, a gyroscope mounted in the vehicle for relative movementtherebetween, driving means for rotating the compass in azimuthrelatively to the vehicle, and means actuated by the relative angularmovement between the gyroscope and vehicle for controlling said drivingmeans to operate the compass in a direction reverse to the angularmovement to maintain it fixed in azimuth.

14. A mechanism for controlling a compass. including a. magnetic compassmounted in a vehicle and adapted to normally respond to magneticinfluences, a gyroscopeI mounted in the vehicle for relative angularmovement therebetween, and means controlled by the gyroscope for turningthe compass in azimuth proportionately and reversely to the angularmovement between said gyroscope and the vehicle to maintain said compassfixed in azimuth.

15. In combination, `a magnetic` compass, af

gyroscope normally disconnected from the compass, and means forperiodically connecting the compass and gyroscope together forcontrolling the former by the latter.

16. In combination, a magnetic compass mounted in a vehicle for freeresponse to mag-- netic influences, a gyroscope` mounted in said vehiclefor relative angular movement therebetween, and means effective uponsaid relative angular movement for connecting r the compass andgyroscope together for controlling the former 17. A method ofcontrolling a Imagnetic compass mounted on a moving aircraft and subjectto deviations caused by disturbing forces acting on the compass, whichforces are produced by changes occurring in a lfactor contributing yinthe maintenance of a predetermined condition of flight of said aircraft,which method consists in subjecting said compass to gyroscopic controlduring the time that said changes are occurring.

for connecting the compass and gyroscope together during the time thatsaid changes are oc-g curi-ing.

19. In combination, a magnetic compass mounted on an aircraft fornormally free re sponse to the earth's magnetic field and subject todeviations caused by disturbing forces acting on the compass, whichforces are produced by changes in a factor contributing in themaintenance of a predetermined condition of flight of said aircraft, anazimuth gyroscope disassociated from the compass, and means responsiveto said'changes for connecting the compass and gyroscope together duringthe time that said changes are occurring.

20. In combination, a magnetic compass mounted on a craftfor normallyfree response to influences of the earth's magnetic field, directionalcontrol, means disassociated from the compass, and means effective uponangular movement of the craft about one of vits axes for connecting thecompass and directional control means together to prevent deviations' ofsaid compass which otherwise might occur.

21. In combination, a magnetic compass mountefd on a craft for normallyfree response to influences of the earths magnetic eld, gyroscopicdirectional control means disassociated from the compass, and meanseffective upon angular movement of the craft about oneof its axes forconnecting the compass and directional control means together to preventdeviations of said compass which otherwise might occur.

22. In combination, a magnetic compass having a compass card pivotallymounted for normally free response to the earth's magnetic field,directional control means disassociated from said card, andmeanseffective upon the occurrence ofa predetermined condition or effectwhich is 50 adapted to cause a deviation of the card for connecting saidcard and directional control means together to prevent such deviationsof said card which otherwise might 'occu-r. a

23. In combination, a magnetic compass having a compass card pivotallymounted for normally free response to the earths magnetic field,gyroscopic directional control means disassociated from said card, andmeans effective upon the occurrence of a predetermined condition oreffect which is adapted to cause deviation of the card for connectingsaid card and directional control means together to prevent suchdeviations of said card which otherwise might occur.

24. In combination, a magnetic compass, a gyroscope normallydisconnected from the compass, and means for connecting the compass andgyroscope together at selected times whereby the compass is normallyfree to respond to magnetic ing the compass and gyroscope to and fromeach other for controlling the former by the latter while connected, toprevent deviations ofthe compass which would otherwise be produced.

5 26. The method of controlling a magnetic compass mounted in anaircraft for normally free response only to the earths magnetic eldwhile the craft is' ilying a straight course, which comprises subjectingthe compass to gyroscopic 10 control to hold the compass elementsubstantially xed while the craft is turning about one of its axes, andreleasing said compass from said gyroscopic control when the aircrafthas ceased turning.

27. The method of controlling a magnetic compass mounted in a vehiclefor normally free response only to the earths magnetic eld, whichcomprises subjecting the compass to gyroscopic control to hold thecompass element substantially 20 xed in azimuth while the vehicle isturning,

and releasing said compass from said gyroscopic control when theaircraft has ceased turning.

28. A mechanism for controlling a compass,

including in combination, a magnetic compassr mounted in a vehicle andadapted to normally respond freely to magnetic inuences, an azimuthgyroscope mounted in the vehicle, and means responsive to turning of.the vehicle for connecting the compass to the gyroscope for `maintainingthe `compass iixed in azimuth during the turning.

29. A method of controllingsa magnetic com` pass in a vehicle, whichcomprises selectively subjecting the compassto gyroscopic control tohold the compass element substantially iixed in azimuth, andinterveningly releasing the compass element to the inuence of the earthsmagnetic eld.

30. The method of controlling a magnetic compass in a vehicle, whichcomprises periodically subjecting the compass to gyroscopic control tohold the compass element substantially xed in azimuth, and interveninglyreleasing the compass element to the inuence of the earths magnetic eid.

31. The method of controlling a magnetic compass in a vehicle, whichcomprises intermit' tently subjecting the compass to gyroscopic con- 9trol to hold the compass element substantially fixed in azimuth, andinterveningly releasing the compass element to the inuence of the earthsm'agnetic field.

32. The method of controlling a magnetic compass, which comprisesselectively subjecting the compass to and releasing the same fromgyroscopic control to ho'ld the compass element "substantially fixed inazimuth.

disconnected from the direction indicating device, and means forconnecting and disconnecting the direction indicating device and thegyroscope to and from each other for controlling the former by thelatter while connected, to Iprevent the error which would otherwiseoccur.

35. In combination, a free directional gyroscope, a compass cardrotatably mounted adjacent said gyroscope, a driving element mounted onthe gyroscope to turn in azimuth therewith and having a mechanicaldriving connection with said card to turn the latter as the .gyroscopeturns relative to its mounting, and means for interrupting said drivingconnection without disturbing said gyroscope.

36. In combinatiom'a free directional gyrov scope, an indicating cardhaving side-reading graduations on the periphery thereof and rotatablymounted adjacent the gyroscope for rotation about a vertical axis, adriving element mounted on the gyroscope to turn in azimuth therewithand having a mechanical driving connection with the card to turn thelatter as the gyroscope turns relative to its mounting, and means forinterrupting said driving connection without disturbing the gyroscope.-

lFRANCIS A. WADE.

ADQLF URFER.

